This application requests partial support for "The Third International Conference on the Interaction of Radiation Therapy and Systemic Therapy" to be held in Asilomar, California, March 9th-12th, 1990. The specific request is for partial costs of (1) travel for the 6 keynote speakers and 10 junior investigators, and of (II) preparation of the Program book of extended abstracts and publication of the proceedings of the meeting. Combined modality therapy is in wide clinical use for the treatment of cancer. The approach has great potential, since it includes therapies directed to eliminating occult metastases as well as to increasing therapeutic index for treatment of the primary tumor. Combined modality treatment has led to improvement in outcome for patients with some types of malignancy, but for others clinical promise will only translate into major therapeutic gains when mechanisms of interaction between modalities are understood, and when appropriate clinical trials are carried out. Between the first 2 conferences in 1978 and 1986, there was a transition from showing beneficial effects in model systems (phenomenology) to an early but incomplete understanding of mechanisms, together with an appreciation for the limitations of some of the current clinical research. Recent advances in understanding mechanisms of therapeutic resistance and other biological factors, as well as requirements for valid clinical trials, make the proposed conference particularly timely. The conference will be structured into 6 sessions, each of which will stress mechanistic science and critical evaluation of results from the laboratory to the clinic. Original research will be presented as extended abstracts with 4-minute mini-presentations (limited to 4 slides), and a large amount of discussion after each set of presentations. Keynote speakers (1 per session) will be selected as outstanding early to mid- career scientists, while more senior individuals will co-chair the sessions and lead the discussion. The site, Asilomar, has been chosen because of its relative isolation, thus stimulating informal interaction among scientists and clinicians, and because the low price of (shared) accommodation will allow the attendance of many junior investigators. The proceedings of the meeting will be published, after peer review, within one year; this will allow rapid dissemination of new information relating to experimental and clinical aspects of combined modality treatment.